1. Field of the Invention
The present invention relates generally to variable displacement compressors. In particular, the present invention is directed towards variable displacement compressors in which a valve assembly is operationally coupled to a orifice mechanism to control a pressure within a crank chamber of the compressor.
2. Description of Related Art
Known variable displacement compressors, used in automobiles, such as the compressor described in Japanese Publication No. JP-Y S63-32933, include a swash plate or a cam plate positioned within a crank chamber, and a piston which reciprocates within a cylinder bore. An inclination angle of the plate varies in response to a pressure in the crank chamber, and the inclination angle determines a stroke length of the piston. Specifically, when the pressure in the crank chamber increases, the inclination angle and the stroke length of the piston decreases. Similarly, when the pressure in the crank chamber decreases, the inclination angle and the stroke length of the piston increases. Moreover, when the piston moves away from the suction chamber, the piston draws a refrigerant, e.g., a liquid refrigerant or a refrigerant gas, from the suction chamber into the cylinder bore. Similarly, when the piston moves toward the suction chamber, the piston compresses the refrigerant within the cylinder bore, and discharges the compressed refrigerant into a discharge chamber.
Such known compressors also include a first path which allows refrigerant communication between the crank chamber and the discharge chamber, and a second path which allows refrigerant communication between the crank chamber and the suction chamber. Moreover, a valve assembly controls the flow of refrigerant within the first path, and an orifice mechanism controls the flow of refrigerant within the second path. When a valve of the valve assembly is open, the compressed refrigerant inside the discharge chamber flows into the crank chamber, and the inclination angle decreases. Similarly, when the area of an opening of an annulus of the orifice mechanism increases, the refrigerant flows from the crank chamber to the suction chamber, and the inclination angle also increases.
In the known compressors, the area of the opening of the annulus and the rate at which the refrigerant flows from the crank chamber to the suction chamber depends on a difference between the pressure in the suction chamber and the pressure in the discharge chamber. Specifically, when the difference between the pressure in the suction chamber and the pressure in the discharge chamber increases, the rate at which the refrigerant flows from the crank chamber to the suction chamber increases. Similarly, when the difference between the pressure in the suction chamber and the pressure in the discharge chamber decreases, the rate at which the refrigerant flows from the crank chamber to the suction chamber decreases. Nevertheless, when the difference between the pressure in the suction chamber and the pressure in the discharge chamber is less than a predetermined pressure differential, the area of the opening of the annulus is closer to the minimum area than the maximum area, and the inclination angle is less than a predetermined inclination angle. When a user of the automobile then signals to decrease a temperature within the automobile from an actual temperature to a predetermined temperature, the difference between the pressure in the suction chamber and the pressure in the discharge chamber increases, e.g., because the crank chamber pressure decreases. As such, the inclination angle also increases, and the area of the opening of the annulus increases. Nevertheless, a predetermined amount of time expires before the inclination angle increases to the predetermined inclination angle, and the area of the opening of the annulus increases to the maximum area. Consequently, the predetermined amount of time expires before a temperature of air dispensed from the compressor is about equal to the predetermined temperature.